A touch of weevil

Continental arrivals are causing havoc, writes Kylie O'Brien

Kylie O'Brian

12:01AM BST 12 Oct 2002

As if we didn't have enough to worry about, last week we heard that two species of vine weevil new to Britain were discovered in London.

Otiorhynchus armadillo and Otiorhynchus salicicola are counted among the most serious garden pests in southern Europe and are, according to Max Barclay, curator of beetles at the Natural History Museum, now prevalent in Chelsea, Victoria, Pimlico and Fulham. "They have been very destructive in south west London gardens," he warns, "and it does look like they're here to stay."

But how worried should we be? The weevils are thought to have been brought here in imported plants, and are thriving despite the colder British climate. One potential headache is the speed with which they spread: Barclay found Otiorhynchus armadillo in 1998 on the window of a Chelsea department store; since then it has become the most common species of vine weevil in south west London. They have now been found in Surrey, Cardiff and Edinburgh.

Another problem is that no one knows how much destruction they might do and how well they will adapt. Barclay warns that numbers are growing faster than those of the native vine weevil.

"Someone in Pimlico had a new roof garden designed and planted earlier this year," he said. "I saw it in May, and it looked beautiful. When I returned in June, it was completely devastated. They bought soil and plants from the same place, so the soil must already have been infested. While I was there I collected 60 or 70 weevils in 20 minutes; I've never known our own to reproduce so effectively."

Related Articles

The good news is that the same forms of pest control - imidacloprid or nematodes - that work on our native black vine weevil, Otiorhynchus sulcatus, will work on the new arrivals. And natural predators may help.

"Things might change when the weevils have had a chance to settle in ecologically," says Barclay. "Native predators haven't learnt how to hunt for them yet, and birds will soon twig on to the fact that there is an excellent source of food in, for instance, cherry laurels, which vine weevils love."

Andrew Salisbury, an RHS entomologist, says it's too soon to know how to react: "Whether it will move out of sheltered urban habitats or urban areas is an unknown." He says it's important to keep it in prespective: "It's another pest, but, on the other hand, new ones come into Britain all the time."

Salisbury believes that, among other predators, ground beetles may help keep numbers down: "They have been shown to eat vine weevil eggs, larvae and even adults of the native species - so it has to be assumed they will do the same to the introductions."

Identification

The two new species, Otiorhynchus armadillo - "armadillo weevil" and Otiorhynchus salicicola "willow weevil" look similar to our native black weevil, with a couple of important differences. Look at the legs: the black weevil has small hooks, or spines, on the side of the front legs; the new ones don't. The black weevil (which is up to 11mm long) is smaller and darker, the European weevils are both paler and more rounded in shape.

If you think you have either of the new weevils, or you would like more information, write with a specimen to Max Barclay, c/o The Insect Identification Service, Natural History Museum, Cromwell Road, London SW7 5BD. Tel: 020 7942 5000.

Control

Use nematodes watered into soil which is above 60C, or the chemical imidacloprid, available as Vine Weevil Killer from most garden centres.